1. Field of the Invention
The present invention relates to integrated-circuit (IC) memory chips and, more particularly, to an enhanced integrated circuit memory chips that incorporate additional functions in a standard memory package.
2. Prior Art
Portable electronic devices such as laptop computers, cell phones, personnel digital assistants (PDA's), handheld or portable game consoles from companies such as Nintendo, Sony, and other portable electronic devices, all use standard integrated-circuit memories. Standard memories include, but are not limited to: static random access memory (SRAM), pseudo-SRAM, dynamic random access memory (DRAM), Flash memory, electronically erasable programmed read only memory (EEPROM), electronically programmed read only memory (EPROM), read-only memory (ROM), and others. These various types of standard memories are currently fabricated by a number of memory manufacturers such as, for example, Samsung, Sony, Mitsubishi, NEC, Micron, Infineon, Cypress, IDT, UMC, Hyundai, and others. Because standard memories are commodity products that are consumed in very large quantities, there are industry standards that define various physical aspects and electrical functions of various standard types of memory packages such as a small outline package (SOP), a thin small outline package (SOP), a shrink thin small outline package (STSOP), and a ball grid array (BGA) package. For packages with pins such as the various types of small outline packages (SOP), an industry standard includes the pin-layout configuration. For BGA packages, an industry standard includes the ball size, pitch, and layout.
An important aspect of memory products is that a successful memory product tends to become standardized in an industry. Industry standards are preferred by original equipment manufacture (OEM) manufacturers that are buyers of the standard memories and that prefer to have multiple suppliers supplying them with the same part so that the OEM manufacturers can have multiple sources for competitive pricing, scheduling, and other considerations. Standardization is also endorsed by memory manufacturers, especially for the later memory manufacturers that want to get into customer sockets for which there are already incumbent suppliers. To compete with the incumbent suppliers, the later memory manufacturers have to maintain the same basic fit, form, and function of a standard integrated-circuit memory package, or at least minimize the differences between their product and the standard. Fit of a memory package is the size of a memory integrated-circuit package in all three dimensions and the layout configuration of the memory integrated-circuit package. Form is the type of package and the package material, such as plastic or ceramic. Purchasing a component that conforms to an industry standard minimizes the work that a customer OEM manufacturer needs to do to accommodate using an integrated circuit from a later memory manufacturer. A memory integrated circuit of a later memory manufacturer typically performs the same memory functions as the memory integrated circuits of an incumbent supplier. The later memory integrated circuits often have improvements in speed, power consumption, and performance to make them more attractive than those of the incumbent suppliers.
Process technology for memory fabrication keeps improving so that memories double in density and size every few years. As an example, in the wireless communication industry, the memory requirements for a cell-phone handset have increased from a typical 1 Megabit SRAM together with an 8 Megabit Flash memory to a 2/4/8 Megabit SRAM together with 16/32/64 Megabits of Flash memory. The package fit and form for memory packages has evolved from a SRAM package and a separate Flash memory into a Flash/SRAM combination package that puts the SRAM and the Flash memory in the same package module, such as ball grid array (BGA). All BGA Flash/SRAM combinations have a similar typical package size, type, ball pitch, and layout, and are interchangeable with other manufacturers' products for particular customer uses, as previously discussed.
As cell phone designs have moved from a 2G second generation to a 3G third generation and beyond, memory requirements for the new cell-phone designs have further increased. In RAM designs, SRAMs are evolving into pseudo-static memories that have a DRAM core cell and a static RAM I/O interface. Eventually, as memory size and density further increase, SRAMS will evolve into pure DRAMs for cost reasons.
New wireless communication appliances, such as cell phones, PDAs, game consoles, and other portable devices require increased memory-array sizes. Concurrent with the requirement for increased memory-array size, a number of additional functions are being added to wireless telecommunication appliances as cell phone designs have gone from an analog to a digital format New cell phone designs now are provided with high-fidelity sound quality and with audio signal functions such as MP3 music, video, and other multimedia functions. Other additional capabilities that are being designed into wireless communication appliances include data streaming for accessing the internet, global positioning systems (GPS) for real-time map direction and locations, and Bluetooth appliances for short distance wireless communication between wireless communication appliances. Other additional capabilities are being introduced by IC suppliers and added to cell-phones and other wireless communication appliances.
The wireless communication industry has expanded rapidly in the 1990's. In 1999, the global sales of cell phones were about 280 million units. In 2000, the global sales of cell phones had grown to over 400 million units and are expected to approach 500 million units in 2001. With the explosion of the Internet, the global, internet-driven economy is motivating and enabling the burgeoning mobile data content and applications markets.
FIG. 1 is a chart that illustrates the evolution of various generations of mobile communication systems. The wireless-content business has evolved from primarily voice communication in the first 1G and the second 2G generations to digital in the 2.5 G generation. The third 3G digital multimedia generation provides multimedia wireless devices such as cell phones and wireless personal digital assistants (PDA's) such as Palms, and palmtop and laptop computers. These 3G multimedia wireless devices provide a high-resolution, color video display with quality comparable to a television (TV) set or to a personal computer (PC) monitor. To minimize the amount of data transfer required for these multimedia wireless devices, data compression and decompression (CODEC) techniques, such as Moving Picture Expert Group-4 (MPEG-4), are used extensively for streaming audio-visual information to provide applications such as content-based access for digital storage media, digital audiovisual communication, and other applications. Companies have developed CODEC digital signal processor (DSP) chips that enable transmission and reception of high-quality audio and video signals over the Internet and through next-generation mobile handsets. These CODEC DSP chips use a quarter-common-intermediate format (QCIF) standard screen size of 176 by 144 pixels for video reproduction in videophones at a typical rate of 10-15 frames per second.
Typical wireless cell phone devices implement the CODEC DSP within the cell-phone baseband IC chip using an embedded controller/processor in conjunction with analog to digital (A-to-D) and digital to analog (D-to-A) converters.
In addition to CODECs, baseband (BB) IC suppliers are also incorporating one or more additional features such as Global Positioning Systems (GPS) and Bluetooth local wireless communication features into their baseband integrated circuits. To run all of these additional functions, more powerful processors from manufacturers such as ARM, Intel, and MIPs, etc., are required to run at high clock rate to meet the processing requirements for additional functions. Running more powerful processors at high data rates uses a lot of power, which can rapidly drain a battery and thereby reduce the active operation time of a mobile handset.
Furthermore, in order to access data stored in a handset integrated-circuit memory for data encoding/decoding, data compression/decompression, and display purposes, the baseband chip has to communicate with a memory chip every clock cycle on the printed-circuit data busses between the separate baseband integrated-circuit package and the memory integrated-circuit package. To effectively drive the printed-circuit board (PCB) data busses between the separate baseband integrated-circuit package and the separate memory integrated-circuit package at a high enough data rate, integrated-circuit output drivers on each integrated circuit have to provide sufficient current drive to the PCB data busses. This further increases power consumption and drains the battery.
FIG. 2 shows a simplified system architecture for a prior-art multimedia wireless system 10 that is used in a typical wireless communication device, such as a cell phone. The system typically includes several discrete integrated-circuit packages that communicate with each other through a bus on a printed-circuit board, represented as a PCB bus 12. A radio frequency (RF) integrated circuit 14 transmits and receives RF signals through an antenna 16. Data signals are sent to and from the RF integrated circuit 14 on the PCB bus 12. A standard memory integrated-circuit package 18, such as a SRAM or a Flash/SRAM combination memory, that has its terminals connected to the system bus 12. A liquid crystal display (LCD) controller integrated circuit 20 has its terminals connected to the system bus 12 and provides signals for displaying text on a suitable LCD-display device 21, such as a LCD text display screen. A baseband (BB) integrated circuit 22 is provided with a microcontroller core, such as provided by ARM or MIPs.
FIG. 2 illustrates that most of the additional functions requited in a typical cell phone are typically provided by the baseband integrated circuit 22. Additional capability, such as, for example, MPEG4 capability, is provided as a soft-wired or hardwired function that is embedded in hardware and/or software of the baseband integrated circuit 22.
In the case where the base-band integrated circuit cannot accommodate the additional functions, one or more additional special function integrated circuit packages, illustratively represented as 24, are provided, such as, for example, a GPS integrated circuit chip package to provide desired additional functions. To provide even more special, dedicated functions, a baseband chip set is provided that conventionally includes a microcontroller and one or more additional DSP integrated circuits.
It can be appreciated that using additional integrated circuits of a baseband chip sets is not preferred by cell-phone handset manufacturers. Additional integrated circuits increase the size of a printed circuit in the cell-phone, increase the cell-phone weight, require more inventory and control of the additional integrated circuits, and add additional cost for the additional integrated circuits. For these reasons, as more advanced models are developed by the cell phone industry, the trend is to integrate as many functions as possible into a single multi-function base-band integrated circuit and to eliminate special-function integrated circuits or chip sets.
However, it should also be appreciated that the cell-phone industry trend toward adding more functions to a single baseband integrated circuit or to a baseband chip set increases the complexity of the base-band integrated circuit or chip set and requires additional signal processing power in the baseband integrated circuit. For example, the basic microcontroller unit used in the baseband chips has changed from an ARM 7 to 9 to an ARM 10 to 11, while the clock cycle rate has gone from tens of megahertz to a few hundred Megahertz These large increases in performance requirements for a single baseband integrated circuit or a baseband chip set have increased the size, number, complexity, and cost of baseband integrated circuits. It should also be appreciated that the power requirements for a more complex baseband integrated circuit have also increased. In future 3G and beyond cell-phone designs, the cellphone or wireless appliance will be required to be constantly on with the baseband integrated circuit being required to be constantly running at a very high clock rate. This will significantly increase the power consumption of the baseband integrated circuit and will rapidly drain a cell-phone battery, reducing the usable time between cell-phone battery charges.
Consequently, a need exists for a technique that adds additional memory-intensive functions into portable electronic devices, such as a wireless appliance or a cell phone, but that does not increase package count and power consumption while keeping substantially the same fit and form as a standard memory integrated circuit.